1. Field of the Invention
The present invention relates to refrigeration and air conditioning systems, and more particularly, to an improved system utilizing a modulating valve in conjunction with a subcooler/economizer for controlling the temperature of a refrigerant in the system. The present invention finds particular application in conjunction with supermarket food refrigeration systems, and it will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications.
2. Discussion of the Art
Commercial refrigeration and air conditioning systems frequently employ multiple evaporators to meet specific cooling needs. Often the evaporators and their associated expansion valves are remotely located relative to other components of the refrigeration system in order to cool refrigeration cases. As a result, lines, conduits, or piping leading to the remotely located evaporators cover great distances and decrease the overall efficiency of the refrigeration system. With the increasingly high cost of energy, it is generally desirable to increase the efficiency of commercial refrigeration systems.
One method of combating the inefficiencies associated with remotely located refrigeration cases is to use subcooling. Subcooling the liquid refrigerant of a refrigeration system increases the refrigerant effect, or the quantity of heat absorbed in the refrigerated space per unit mass, without increasing energy input to the compressors. Thus, subcooling increases the efficiency of the system and reduces the power requirements of the system per unit of refrigerating capacity.
Even with subcooling, inefficiencies may still exist. For example, pipes running from the condenser to the evaporators are often not insulated due to the remote location of the evaporators. As a result the refrigerant flowing through these pipes is often below the dew point and causes sweating or condensation of water on the pipes. As is well known, sweating decreases the efficiency rating of the refrigeration system.
Therefore, it is desirable to provide an improved refrigeration system with controlled subcooling for overcoming these problems and others.
The present invention relates to an improved refrigeration system utilizing a modulating valve in conjunction with a subcooler/economizer for controlling the temperature of a refrigerant in the system.
In accordance with one aspect of the present invention, the refrigeration system comprises a compressor, a condenser, one or more refrigeration cases, and an evaporator for cooling the refrigeration cases. The compressor is interconnected to the condenser, the condenser is interconnected to the evaporator, and the evaporator is interconnected to the compressor in a closed loop.
The refrigeration system further includes a subcooler operatively disposed downstream of the condenser and upstream of the evaporator. The subcooler includes an expansion valve for expanding a first portion of the condensed refrigerant exiting the condenser and using the expanded refrigerant for subcooling a second portion of remaining unexpanded refrigerant exiting the condenser. The unexpanded refrigerant flows to the evaporator after subcooling. The subcooler also has a return line in parallel with the evaporator for returning the expanded refrigerant to the compressor after subcooling.
A modulating evaporator pressure regulator valve is located on the return line. The modulating valve controls a suction gas pressure to the compressor which controls the liquid temperature of the refrigerant entering the evaporators. The modulation of the valve occurs in response to a dew point in the ambient environment or store and/or the temperature of the liquid entering the evaporators which efficiently cools the refrigeration cases to a desired temperature while preventing line sweating.
In accordance with another aspect of the present invention, the modulating valve modulates in response to the ambient temperature in the store.
In accordance with another aspect of the present invention, the modulating valve modulates in response to the temperature of the expanded refrigerant entering the subcooler.
In accordance with another aspect of the present invention, the subcooler is removed.
A primary advantage of the present invention is the provision of a refrigeration system that allows for a smaller compressor without reducing the refrigeration capacity of the system.
Another advantage of the present invention is the provision of a refrigeration system that can be operated remotely.
A further advantage of the present invention is the provision of a refrigeration system that allows for smaller, less expensive refrigeration lines.
Another advantage of the present invention is the provision of a refrigeration system that does not require insulated lines, yet limits sweating of the lines.
Still another advantage of the present invention is the provision of a refrigeration system that requires less refrigerant in the system.
Further advantages and benefits of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description.